             z-corrections (ref nil)
             last-wake-time (atom (clock-ms))
             start-time (clock-ms)
-            init-auto-shutter (. mmc getAutoShutter)]
+            init-auto-shutter (. mmc getAutoShutter)
+            default-z-position (get-z-position (. mmc getFocusDevice))]
     (let [acq-seq (generate-acq-sequence settings)]
        (def acq-sequence acq-seq)
        (execute (mapcat #(make-event-fns % out-queue) acq-seq))

				(+ (or (get-in event [:channel :z-offset]) 0)
				   (or (get @z-corrections z-drive)
				     (:slice event)
				     (get-z-stage-position z-drive))))
      (assoc-in [:postion :axes z-drive] nil))
    event))
   

(declare interrupt-requests)
(declare z-corrections)
(declare init-auto-shutter)
(declare default-z-position)

;; metadata

